Messages in this thread | | | Date | Fri, 27 May 2005 14:48:37 +0200 | From | Ingo Molnar <> | Subject | Re: RT patch acceptance |
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* Andi Kleen <ak@muc.de> wrote:
> [...] Even normal kernels must have reasonably good latency, as long > as it doesnt cost unnecessary performance.
they do get reasonably good latency (within the hard constraints of the possibilities of a given preemption model), due to the cross-effects between the various preemption models, that i explained in detail in earlier mails. Something that directly improves latencies on CONFIG_PREEMPT improves the 'subsystem-use latencies' on PREEMPT_RT. Also there's the positive interaction between scalability and latencies as well.
but it's certainly not for free. Just like there's no zero-cost virtualization, or there's no zero-cost nanokernel approach either, there's no zero-cost single-kernel-image deterministic system either.
and the argument about binary kernels - that's a choice up to vendors and users. Right now PREEMPT_NONE is dominant, so do you argue that CONFIG_PREEMPT should be removed? It's certainly not zero-cost even on the source code, witness all the preempt_disable()/preempt_enable() or get_cpu()/put_cpu() uses.
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